A restaurant no-one wants to talk about. Shout its name in the street and you may very well be lynched, a hate mob rugby tackling you in seconds, gagging your mouth and forcing you to swear allegiance to the cause: Sushi T****. “Thou shalt not reveal its name or mention it to your friends. How will we ever get a seat again if you go blabbing to all your mates? Put them off the scent, tell them fibs, send them elsewhere. This place is ours.”

Some of the best sushi restaurants in London are usually such an arse to get to. It goes something like this: “Discovered a great new Sushi place.” “Oh really? Where is it?” “Ealing.” F***ing Ealing. So far West that East London boys like this one start getting twitchy at West Acton, as we hurtle off the Underground map. Sushi Hiro was a real schlep when it was around, ridiculously short opening hours only adding to the trauma. I remember being titillated by a sake Slush Puppy and a great husband and wife team at Sushi-Say in Willesden. Willesden doesn’t encourage repeat visits. Acolytes hunt down the much vaunted Yashin, Dinings and the tiny Sushi of Shiori. Sushi forces you to make a serious effort to find the good stuff.

Harumi and Toru Takahashi arrived last month in the tiny alleyway in Farringdon with space for so few covers it requires a double-take. Seven seats at the bar. Sushi and sashimi only, no miso, no tempura, no hot food, just fish sourced largely from Billingsgate market and laid out like a perfect art installation ready for slicing to order. There’s a purity to the set-up which is unnerving. Toru has flirted with the kitchens of Nobu after apprenticing in Kobe, opening here with wife Harumi.

It feels like gatecrashing a private party. At Sushi Tetsu you’re a part of the dance, you’re on stage with the other diners, Toru and Harumi loving every moment - if the staff are having a good time, chances are you’ll be having a good time too. The first piece of the seven piece sushi ‘Omakase’ menu (£28) is presented, Harumi urging to eat up quickly: each piece presented one at a time, like a votive offering, prompting thoughts of “bugger me, we’re playing with the big boys here.”

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Sea bream (Tai) - Lovingly brushed with soy by the fingers of Toru-san. Something disturbingly sensual about this. No need for soy dipping, the job has been done. Jolt to the senses, sushi landscape shifting from the kick-off – clear straight away that this place is ‘different gravy’. Toru’s vinegared rice (sushi-meshi) is exceptional. A blistering start.

Salmon (Sake) – Bonkers. When fish starts to assume the texture of butter you know there a some ‘whack’ skills going on in the sourcing and preparation. Silken, ephemeral, melting. Salmon shape shifting in the mouth to butter. Infernal sushi wizardry going on here. Spooky.

Sweet shrimp (Ama-ebi) – Pale little puppies bound with nori. Looking nothing spesh, they delight with sweetness. Could pop a few of these off in one sitting with supporting fire from many bottles of Asahi.

Squid (Ika) - The hardcore sushi lovers twitch and fret over this one, bemoaning that our squid never has the tenderness of that found in the best spots in Tokyo. Perhaps not, but this had more than enough to keep me interested, a haunting creaminess. Blowtorch comes out for this one, one of many intermittent moments of Toru Theatre – cheeky smile as he sees the squid curl up adds to the fun. Concentration on his face as he scores the squid in tiny bursts is pure theatre.

Lean tuna (Akami) – Tuna Jim, but not as we know it. This was the lean cut rather than the fatty ‘O-toro’ frothed over by the hardcore advocates of tuna (and rightly so), and comes out looking like a jewel, a ruby coloured slice of fish. Captivating silky texture.

Razor clam (Tairagai) – Enter citrus fruit sudachi, a tiny lime wannabe that hasn’t eaten its Weetabix. A pin-prick amount placed by Toru on this nigiri to help cut through sweet razor clam.

Prawn (Ebi) - Blowtorch moment as Toru blasts the underside briefly, adding a whack of smokiness to a bouncy sweet prawn. Different planet to most fridge cold, tasteless prawn nigiri served elsewhere.

Razor clam maki - After the masterclass that precedes the roll served at the end, this fades into the background and feels pedestrian (even though clearly not), and the hit of menthol from a piece of shiso leaf in each piece starts a conversation with Harumi about the little flourishes added by Toru.

Eel hand roll (Unagi) – Acted as dessert as we weren’t in the mood for eggy Tamago.

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The most startling thing as a sushi ingénu about this restaurant experience was the pace of the meal. It’s a sushi improv gig as Chef Toru gauges each placing, where in the meal they’re at, and fires into action. Seven pieces of nigiri and a couple of extras effortlessly spans two hours. There are delicious moments where he’s thinking on his feet, cogs whirring, deciding what to prepare next. It’s almost “does this guy know what he’s doing, is it all under control?”. Of course he is, there’s a Zen calmness about him, as if he’s using ‘The Force’ – he probably is.

It feels like ‘Tetsu’ is playing in a different league entirely to the other supposed Grand Cru of London sushi joints. There’s a generosity oozing from Toru and Harumi that is infectious. I spent twice as much as I wanted to (£65 with five Asahi) and didn’t give a damn. It was worth every shekel. I was ready to leave a blank cheque: mate, just fill in the numbers, I don’t care. That’s a rare and quite magical feeling to have in any restaurant.